The role of animal behaviour in the study of endocrine-disrupting chemicals

Behavioral responses of the estuarine calanoid copepod Eurytemora affinis to sub-lethal concentrations of waterborne pollutants

Estuarine waters contain a variety of chemicals which affect to various extents the behavior of aquatic organisms. Little is known, however, on the behavioral response of copepods. The present study shows the results of laboratory experiments investigating the immediate effects of sub-lethal concentrations of three commonly found contaminants on the three-dimensional swimming behavior of the estuarine calanoid copepod Eurytemora affinis. Nonylphenol at 2 μg L⁻¹, cadmium at 45 n gL⁻¹ and a mixture of low to medium molecular weight polycyclic aromatic hydrocarbons at 40 ng L⁻¹ all affected the swimming behavior of E. affinis adults, increasing both swimming speed and activity. In most cases, effects were observable within 30 min of exposure and persisted or faded during a period of depuration in uncontaminated water of similar duration. In ovigerous females exposed to Cd and PAHs, effects appeared to be more pronounced during the depuration period, suggesting that carrying ovisacs may impair recovery. We quantified differences in the distribution of swimming speed values by considering the relative frequencies of periods of break, slow and fast swimming and we observed a trend toward faster movements in the presence of pollutants. The degree of trajectory complexity, estimated through their fractal dimension, was unaffected by pollutants. Since both narcotic and non-narcotic pollutants induced hyperactivity, our results suggest that changes in behavior after a short-term exposure may be independent of the general mode of action of the chemicals. The increase in speed and activity resembles an escape reaction permitting copepods to evade stressful conditions. Overall, these results indicate that environment-relevant concentrations of pollutants can induce rapid changes in copepod behavior. Since behavioral processes represent a fundamental element in the ecology of copepods, our results raise concern about the effects of background levels of pollution on a major component of the plankton community. The long-term response of copepods to waterborne pollutants, their synergistic effects and their interactions with other environmental factors need further investigation.

Cryptic confounding compounds: A brief consideration of the influences of anthropogenic contaminants on courtship and mating behavior

Contaminants, like pesticides, polychlorinated biphenyls (PCBs), dioxins and metals, are persistent and ubiquitous and are known to threaten the environment. Traditionally, scientists have considered the direct physiological risks that these contaminants pose. However, scientists have just begun to integrate ethology and toxicology to investigate the effects that contaminants have on behavior. This review considers the potential for contaminant effects on mating behavior. Here we assess the growing body of research concerning disruptions in sexual differentiation, courtship, sexual receptivity, arousal, and mating. We discuss the implications of these disruptions on conservation efforts and highlight the importance of recognizing the potential for environmental stressors to affect behavioral experimentation. More specifically, we consider the negative implications for anthropogenic contaminants to affect the immediate behavior of animals, and their potential to have cascading and/or long-term effects on the behavioral ecology and evolution of populations. Overall, we aim to raise awareness of the confounding influence that contaminants can have, and promote caution when interpreting results where the potential for cryptic affects are possible.

Acute exposure to 17α-ethinylestradiol disrupts audience effects on male-male interactions in Siamese fighting fish, Betta splendens

Endocrine disrupting chemicals can have profound effects on the behavior of aquatic organisms residing in polluted waters. Males are especially sensitive to the effects of estrogen mimics and both courtship and aggression may be dramatically reduced by chemical exposure. Population-level impacts may occur if these chemicals decrease the ability of males to obtain mates or defend territories. Exposure might also have far-reaching impacts by interfering with information transfer within a network of individuals. For example, males exposed to an endocrine disruptor may be less sensitive to the presence of an audience. Male Siamese fighting fish were used to examine how short-term exposure to 17α-ethinylestradiol (EE2) alters audience effects on male-male interactions. Males either received a nominal dose of EE2 or remained unexposed and then interacted with an opponent in one of three treatments (female, male, or no audience). EE2 altered audience effects in this study. Opponent-directed gill flaring was lower when a female audience was present compared to when there was a male or no audience in both EE2 and control males. The number of opponent-directed tail beats did not differ as a function of audience type in EE2 males. In contrast, unexposed males increased opponent-directed tail beats when a female audience is present. Therefore, EE2 reduces the ability of males to communicate with multiple individuals simultaneously. If this is the case, endocrine disruptor exposure may alter population structure as selection should favor individuals that are able to readily adjust their signaling behavior as a function of social context.

The effects of short-term exposure to an endocrine disrupter on behavioral consistency in male juvenile and adult Siamese fighting fish

17α-Ethinyloestradiol (EE2) is known to impact courtship and aggression but how exposure affects the consistency with which individuals express these behaviors over time is not commonly addressed. In addition, how juvenile and adult male fish differ in levels of behavioral consistency, both before and after EE2 exposure, is unknown. To examine these questions, juvenile and adult male Siamese fighting fish were presented with a dummy male and dummy female simultaneously both before and after acute exposure to a nominal (15 ng/L) dose of EE2. Multiple trials were conducted to measure how consistent individual differences are affected by age and EE2 exposure. Both female- and male-directed behaviors decreased after short-term exposure to EE2. Juvenile and adult fish differed in the number of female-directed tail beats and bites they performed, with adult fish performing more tail beats and juvenile fish performing more bites. EE2 exposure had a greater effect on consistent individual differences in female-directed than in male-directed behaviors, which may be a byproduct of intense artificial selection for aggression in this species. Repeatability values were lower both before and after exposure in juvenile than in adult fish, suggesting that individuals become more consistent with age. This study suggests that male Siamese fighting fish vary in their sensitivity to short-term EE2 exposure and stresses the importance of examining behavior over multiple time points both within and across age classes to gain a more thorough understanding of the effects of endocrine disruptors on behavior.

Burrowing in the freshwater mussel Elliptio complanata is sexually dimorphic and feminized by low levels of atrazine

The widely used herbicide atrazine (ATR) may have endocrine-associated adverse effects, including on behavior. In this study, 120 adult freshwater mussels, Elliptio complanata, were exposed to ATR at the environmentally relevant concentrations of 1.5, 15, or 150 μg/L. Burrowing depth was evaluated hourly for 6 h and at sacrifice animals were sexed by gonad smear. Female controls burrowed overall approximately 30% less than males, the first report of sexual dimorphism in this behavior. Atrazine at 15 μg/L feminized burrowing in both sexes, in that exposed animals burrowed 20% less than their same-sex controls. Males treated with 1.5 μg /L ATR displayed approximately 20-fold higher vitellogenin (VTG) levels than same-sex controls. Higher concentrations of ATR were not associated with increasing effects. A scatterplot showed a weak binomial curve associating low burrowing with high VTG levels. Taken together, these data suggest a nonlinear dose response in behavioral and physiological feminization produced by ATR and support the need to reconsider the widespread use of this compound.

Sublethal contaminant exposure alters behavior in a common insect: important implications for trophic transfer

This study examined the effects of sub-lethal exposure of the ubiquitous pesticide malathion on the behavior of the model orthopteran species, the house cricket (Acheta domesticus). Increasing concentrations of malathion caused male crickets to increase periods of non-directional movement, such as twitching and grooming, directional movement, and to seek out shelter less. These are all behavioral alterations that may increase the cricket's chances of being preyed upon, and thus have the potential for serious ecological consequences through trophic transfer. This study also revealed that female crickets appeared to be less affected by malathion than their male conspecifics, indicating a potential sex-bias in both susceptibility and possible predator attack.

Relationship between blood mercury levels and components of male song in Nelson's sparrows (Ammodramus nelsoni)

Mercury (Hg) adversely affects the health and behavior of exposed wildlife; however, behavioral effects remain largely unknown. Changes in avian singing behavior may affect a male's fitness because song reveals male quality and thus influences female mate choice and male territory-holding ability. Nelson's sparrows (Ammodramus nelsoni) live exclusively on salt marshes and risk high levels of Hg exposure and bioaccumulation. We recorded songs of male Nelson's sparrows at two locations with different Hg exposure to determine if total blood Hg concentration was related to song characteristics, as previously reported for other species. Males with higher blood Hg levels sang at higher maximum tonal frequency, but blood Hg and site location did not influence low tonal frequency and bout duration, contrary to predictions based on other species. Within the contaminated site, Hg levels were related to bouts per minute and gap duration, such that males at that site sang faster songs. Hg influences hormones and alters brain development, raising questions about specific effects on the brains and singing behavior of male Nelson's sparrows.

Behavioral alteration and DNA damage of freshwater snail Bellamya aeruginosa stressed by ethylbenzene and its tissue residue

To study the sublethal effects induced by ethylbenzene and the capability of a freshwater gastropod Bellamya aeruginosa to take up and depurate ethylbenzene, the snail was subjected to two treatments, a 23-day exposure period followed by a 17-day depuration period. Behavioral alteration, namely retraction response, was observed during the exposure period, and the proportion of retracted snails increased under each treatment as the exposure time prolonged but there was no linear relationship between the retracted proportion and the exposure dose. Such behavioral alteration was probably due to the disturbance of membrane permeability stressed by ethylbenzene. Ethylbenzene uptake in unretracted snails was greater than in retracted snails, while the depuration abilities in the two different responses of snails had no significant difference from each other. Because of the limited capability of snails to detoxify ethylbenzene, the depuration was mainly through a slow excretion process and therefore ethylbenzene was still present in the tissue of snail after 17-day depuration. DNA damage was induced significantly in snails exposed to ethylbenzene, and the levels of DNA damage showed positive time-response and dose-response relationships, and moreover the levels of DNA damage had no difference between the two different responses of snails. There was no linear relationship between the level of DNA damage and the amount of residual ethylbenzene in tissue, which may be related to the adaptation mechanism in snail. Overall, the results suggest that the snail has high capability to take up ethylbenzene and low ability to depurate it, and ethylbenzene has potential genotoxicity to snail.

Effects of environmentally relevant concentrations of the xeno-androgen, methyldihydrotestosterone, on male and female mating behavior in Xenopus laevis

Endocrine disrupting compounds (EDCs) are well known to interfere with the hormone system of aquatic vertebrates and to affect their reproductive biology. 17α-Methyldihydrotestosterone (MDHT) is a widely used model compound for the assessment of androgenic EDCs, because it binds with high affinity to nuclear androgen receptors. It was previously shown to affect various aspects of reproductive biology in aquatic vertebrates, however, evidence for MDHT affecting mating behavior of aquatic vertebrate species is lacking. In order to test the assumption that MDHT affects reproductive behavior of aquatic vertebrates, we exposed male and female Xenopuslaevis to three environmentally relevant concentrations of MDHT (30.45 ng L(-1), 3.05 μg L(-1) and 30.45 μg L(-1)). In males, MDHT at all concentrations led to enhanced levels of advertisement calling and decreased the relative proportions of rasping, a call type characterizing a sexually unaroused state of the male, indicating an increase in sexual arousal of MDHT exposed males. Temporal and spectral parameters of the advertisement call itself, however, were not affected by MDHT exposure. In females, MDHT (30.45 ng L(-1)) did not have any effects, while MDHT at 3.05 μg L(-1) increased female receptivity, increased the duration of time females spent close to the speaker playing male advertisement calls and reduced their latency to respond. MDHT at 30.45 μg L(-1), on the other hand, decreased female receptivity and increased their latency to respond. In summary, this study illustrates that exposure to environmentally relevant concentrations of the androgenic EDC MDHT affects male and female mating behavior of X. laevis. Hence, we suggest that nonaromatizable androgens might play a direct and predominant role in the physiology and regulation of reproduction not only in male but also in female frogs.

Rapid-behaviour responses as a reliable indicator of estrogenic chemical toxicity in zebrafish juveniles

Whereas biochemical and molecular parameters have been well recognised as important "signposts" of individual disturbance to endocrine disrupting chemical's (EDCs) exposure, behavioural endpoints are yet greatly overlooked as a routine tool in environmental risk assessment of EDCs. However, life histories are intimately associated with numerous inter- and intra-specific interactions, which invariably depend on the performance of effective behaviours. Within fish species, one of the most important factors influencing energy turnover earlier in the development is locomotor activity. This essential trait reflects the organism's ability to generate and coordinate the metabolic energy required for both reproductive and non-reproductive behaviours. Inappropriate movement responses due to toxic effects of contaminants may ultimately impact important ecological variables. Therefore, in the present study, the swimming bursts of zebrafish juveniles exposed for 40 d to the synthetic estrogen ethinylestradiol (EE(2)), tested at environmentally relevant concentrations (nominal concentrations of 0.5, 1 and 2 ng L(-1)), were investigated in order to address the potential of rapid-behaviour patterns as an effective response indicator of estrogenic endocrine disrupting chemical's exposure. This synthetic estrogen was selected due to its high prevalence in aquatic ecosystems, ability to mimic natural estrogens and proven record of causing negative effects in fish reproduction. The behavioural responses were compared with established endpoints used in the screening of EE(2) effects at adulthood. Results indicate that zebrafish juveniles' swimming activity was significantly decreased upon EE(2) exposure. Since reduced locomotion of zebrafish may impact foraging, predator avoidance, drift and transport, and even interfere with social and reproductive behaviours, a fitness decline of wild fish populations can ultimately be hypothesized. Furthermore, behavioural endpoints were found to display higher sensitivity to EE(2) than either vitellogenin gene induction or reproductive parameters determined at adulthood. Overall, the findings of this work not only demonstrate the power of high-throughput behavioural responses, able to act as sensitive early warning signals of EDC exposure, but also highlight the potential of behavioural endpoints in providing a more comprehensive and non-invasive measure of EDC's exposure.

Endocrine disruption in white ibises (Eudocimus albus) caused by exposure to environmentally relevant levels of methylmercury

Methylmercury is a globally distributed pollutant and upper trophic level aquatic fauna are at particularly high risk of exposure. Although methylmercury is known to have a number of neurological and developmental effects, relatively little is known about effects on endocrine disruption and reproduction in aquatic fauna, particularly in response to chronic exposure at low concentrations. We experimentally exposed captive white ibises for 3.5 years (2005-2008) to dietary methylmercury at three environmentally relevant concentrations (0.05, 0.1 and 0.3 ppm wet weight in diet). We measured fecal concentrations of estradiol and testosterone metabolites in two consecutive breeding seasons (2007 and 2008). When effects were controlled for stage of breeding, this resulted in altered estradiol and testosterone concentrations in adult breeders of both sexes. Changes in endocrine expression were not consistent over both years, and a clear dose-response relationship was not always present. Endocrine changes were, however, associated at all dose levels with changes in reproductive behavior, reduced reproductive success and altered mate choice in males. Male-male pairing and altered courtship behavior in males were related both to dose treatment and, in 2008, to a demasculinized pattern of endocrine expression. Changes in hormone concentrations of dosed homosexually paired males, when present, were in the same direction but at a higher magnitude than those in heterosexual dosed males. Dosed homosexual males showed decreased testosterone during nest-building and elevated testosterone during incubation when compared with their dosed heterosexual counterparts during the 2008 breeding season. In the same year, exposed males had elevated estradiol during courtship, but had decreased estradiol during other stages in comparison with controls. Dosed females generally showed decreased estradiol and testosterone concentrations compared to controls, albeit not with a clear dose-response effect. Our findings suggest that endocrine disruption due to chronic exposure to even low concentrations of dietary methylmercury may be a widespread mechanism by which reproduction is impaired in wild bird populations.

Short-term exposure to an endocrine disruptor affects behavioural consistency in male threespine stickleback

It has been established that exposure to xenooestrogens can have profound effects on reproductive and aggressive behaviours in aquatic organisms. Studies on the effects of 17α-ethinyloestradiol (EE2) on behaviour, however, rarely examine these effects over multiple trials, across time, or across contexts. In addition, it is possible that individuals vary in their sensitivity to EE2 and individuals may differ in the degree to which their behaviour is affected. The study of consistent individual differences in behaviour has grown in popularity in recent years perhaps because of the evolutionary questions this behavioural variation raises. Adult male threespine stickleback (Gasterosteus aculeatus) from an anadromous population repeatedly received the simultaneous presentation of a dummy male and dummy female conspecific both before and after exposure to a short-term, nominal (15 ng L(-1)) concentration of 17α-ethinyloestradiol (EE2). These before and after measures were then compared against one another as well as against responses of males in a control group that was not exposed to EE2. Courtship, aggression, and nesting behaviours were all affected by EE2 exposure. In addition, behavioural consistency over trials was markedly reduced after EE2 exposure, as shown by lower repeatability values in the after exposure measures and in weaker correlations between the before and after exposure measures in the EE2 group compared to the control group. This suggests that male threespine stickleback vary in their sensitivity to EE2. This study is one of the first to examine the effects of short-term EE2 exposure on behaviour across trials and has important implications for population-level fitness consequences of xenooestrogens.

Concentrations of 17 elements, including mercury, in the tissues, food and abiotic environment of Arctic shorebirds

Exposure to contaminants is one hypothesis proposed to explain the global decline in shorebirds, and is also an increasing concern in the Arctic. We assessed potential contaminants (As, Be, Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Sb, Se, Tl, V, and Zn) at a shorebird breeding site in Nunavut, Canada. We compared element levels in soil, invertebrates and shorebird blood to assess evidence for bioconcentration and biomagnification within the Arctic-based food chain. We tested whether elements in blood, feathers and eggs of six shorebird species (Pluvialis squatarola, Calidris alpina, C. fuscicollis, Phalaropus fulicarius, Charadrius semipalmatus, and Arenaria interpres) were related to fitness endpoints: adult body condition, blood-parasite load, egg size, eggshell thickness, nest duration, and hatching success. To facilitate comparison to other sites, we summarise the published data on toxic metals in shorebird blood and egg contents. Element concentrations and invertebrate composition differed strongly among habitats, and habitat use and element concentrations differed among shorebird species. Hg, Se, Cd, Cu, and Zn bioconcentrated from soil to invertebrates, and Hg, Se and Fe biomagnified from invertebrates to shorebird blood. As, Ni, Pb, Co and Mn showed significant biodilution from soil to invertebrates to shorebirds. Soil element levels were within Canadian guidelines, and invertebrate Hg levels were below dietary levels suggested for the protection of wildlife. However, maximum Hg in blood and eggs approached levels associated with toxicological effects and Hg-pollution in other bird species. Parental blood-Hg was negatively related to egg volume, although the relationship varied among species. No other elements approached established toxicological thresholds. In conclusion, whereas we found little evidence that exposure to elements at this site is leading to the declines of the species studied, Hg, as found elsewhere in the Canadian Arctic, is of potential concern for breeding bird populations.

Effects of pre- and postnatal polychlorinated biphenyl exposure on emotional reactivity observed in lambs before weaning

Humans and animals are exposed to PCBs and influences on developmental and endocrine processes are among the most pronounced effects. In the present study it was hypothesised that exposure to PCBs may interfere with sexually dimorphic behaviour. To test this hypothesis, behavioural studies in developmentally exposed sheep were conducted. Ewes were orally administered PCB 153 (98 μg/kg bw day), PCB 118 (49 μg/kg bw day) or corn oil from conception until delivery. However, because of accidental cross-contamination occurring twice causing a mixed exposure scenario in all three groups, the focus of this paper is to compare three distinct groups of lambs with different PCB levels (PCB 153 high-PCB 153 h, PCB 118 high-PCB 118 h, and low combined group-LC) rather than comparing animals exposed to single PCB congeners to those of a control group. Lambs were tested between 2 and 6 weeks of age. When LC males started the light/dark choice test in a dark box, they spent significantly more time in the dark part of the pen than LC females. This gender-related difference was not found in groups exposed to PCBs. A significant inhibitory effect on the activity level of males exposed to stress of confinement was found in the PCB 118 h group. In a high stress situation females from PCB 118 h and males from PCB 153 h were less active than their gender counterparts. The results support the hypothesis that intrauterine exposure to PCBs can alter sexually dimorphic behaviour of offspring.

Evolution and behavioural responses to human-induced rapid environmental change

Almost all organisms live in environments that have been altered, to some degree, by human activities. Because behaviour mediates interactions between an individual and its environment, the ability of organisms to behave appropriately under these new conditions is crucial for determining their immediate success or failure in these modified environments. While hundreds of species are suffering dramatically from these environmental changes, others, such as urbanized and pest species, are doing better than ever. Our goal is to provide insights into explaining such variation. We first summarize the responses of some species to novel situations, including novel risks and resources, habitat loss/fragmentation, pollutants and climate change. Using a sensory ecology approach, we present a mechanistic framework for predicting variation in behavioural responses to environmental change, drawing from models of decision-making processes and an understanding of the selective background against which they evolved. Where immediate behavioural responses are inadequate, learning or evolutionary adaptation may prove useful, although these mechanisms are also constrained by evolutionary history. Although predicting the responses of species to environmental change is difficult, we highlight the need for a better understanding of the role of evolutionary history in shaping individuals' responses to their environment and provide suggestion for future work.

The effects of radionuclides on animal behavior

Concomitant with the expansion of the nuclear industry, the concentrations of several pollutants, radioactive or otherwise, including uranium, caesium, cadmium and cobalt, have increased over the last few decades. These elemental pollutants do exist in the environment and are a threat to many organisms. Behavior represents the integration of all the anatomical adaptations and physiological processes that occur within an organism. Compared to other biological endpoints, the effects of pollutants on animal behavior have been the focus of only a few studies. However, behavioral changes appear to be ideal for assessing the effects of pollutants on animal populations, because behavior links physiological functions with ecological processes. The alteration of behavioral responses can have severe implications for survival of individuals and of population of some species. Behavioral disruptions may derive from several underlying mechanisms: disruption of neuro-sensorial activity and of endocrines, or oxidative and metabolic disruptions. In this review, we presented an overview of the current literature in which the effects of radioactive pollutants on behavior in humans, rodents, fish and wildlife species are addressed. When possible, we have also indicated the potential underlying mechanisms of the behavioral alterations and parameters measured. In fried, chronic uranium contamination is associated with behavior alterations and mental disorders in humans, and cognitive deficits in rats. Comparative studies on depleted and enriched uranium effects in rats showed that chemical and radiological activities of this metal induced negative effects on several behavioral parameters and also produced brain oxidative stress. Uranium exposure also modifies feeding behavior of bivalves and reproductive behavior of fish. Studies of the effects of the Chernobyl accident shows that chronic irradiation to 137Cs induces both nervous system diseases and mental disorders in humans leading to increased suicides, as well as modification of preferred nesting sites, reduced hatching success and fecundity in birds that live in the Chernobyl zone. No significant effect from caesium exposure was shown in laboratory experiments with rats, but few studies were conducted. Data on radioactive cadmium are not available in the literature, but the effects of its metallic form have been well studied. Cadmium induces mental retardation and psychomotor alterations in exposed populations and increases anxiety in rats, leading to depression. Cadmium exposure also results in well-documented effects on feeding and burrowing behavior in several invertebrate species (crustaceans, gastropods, annelids, bivalves) and on different kinds of fish behavior (swimming activity, fast-start response, antipredatory behavior). Cobalt induces memory deficits in humans and may be involved in Alzheimer's disease; gamma irradiation by cobalt also decreases fecundity and alters mating behavior in insects. Collectively, data are lacking or are meagre on radionuclide pollutants, and a better knowledge of their actions on the cellular and molecular mechanisms that control animal behavior is needed.

Behavioural ecotoxicology, an "early warning" signal to assess environmental quality

BACKGROUND

In this review, the position of behavioural ecotoxicology within the available means to assess the status of marine environments is described as filling the gap for the needed "early warning" signals. A few examples of studies performed since the 1960s are discussed to highlight the sensitivity of these approaches in investigating the effects of chemicals, including priority pollutants and emerging contaminants, relative to conventional toxicity tests measuring survival.

DISCUSSION

The advantage of the behavioural response is due to the integration of biochemical and physiological processes that reflect changes at higher levels of organisation with ecological relevance. Avoidance often represents a behavioural symptom easily detected in many animals exposed to contaminants and would be a useful test to explore more widely. This rapid response would reflect a defence mechanism protective against further exposure and the potential development of more pronounced deleterious effects, whilst in some cases, escape could lead to the relocation of a species with negative consequences. An investigation of the avoidance behaviour of mud shrimp, Corophium volutator, along with the chemical analyses of sediments and amphipods to assess the quality of harbour sediments is summarised. The body burden of the amphipods was 1,000 times lower than the one associated with narcosis, emphasizing the sensitivity of this endpoint. The application of this acute toxicity test is briefly compared to additional work that involved intertidal mussels collected in the field.

CONCLUSIONS

Recent research undertaken with mud snails, Ilyanassa obsoleta, and harbour sediments confirmed the usefulness of the escape behaviour as an assessment tool. However, the limits of the state of knowledge regarding the fate of contaminants in species with the ability to metabolise contaminants is further discussed along with directions to be pursued to address questions arising from the reviewed literature.

Phytochemicals and reproductive function in wild female Phayre's leaf monkeys (Trachypithecus phayrei crepusculus)

Female reproduction is known to be influenced by food availability and its impact on energetic status. However, emerging evidence suggests that the phytochemical content of food may also be an important factor. Here, we investigated this hypothesis, presenting 20 months of data on fecal progestin (fP) patterns in wild female Phayre's leaf monkeys (Trachypithecus phayrei crepusculus). We examined whether (a) the availability of Vitex (a plant known to contain phytochemicals) might be linked to seasonal fP levels, (b) fP levels were associated with female reproductive performance, and (c) reproductive performance might also be linked with energetic status (as measured by physical condition). We collected fecal samples (N=2077) from 10 adult females to analyze estrogen (fE) and progestin (fP) metabolites, behavioral data from 7 cycling females to determine receptivity, and monthly data on Vitex availability and female physical condition. Seasonally elevated fP levels were found in all females, with higher levels when Vitex leaves and fruits were abundant. During the period of high progestins, females had longer cycle lengths and follicular phases, while receptive periods did not change. Nevertheless, when ovulations occurred, females were more likely to conceive. On the other hand, conceptions were also more likely when physical condition was improving, suggesting that the effects of phytochemicals and energetic status on reproduction may be difficult to separate. Although our results support the predicted effects of Vitex on endocrine and reproductive function, future studies with detailed feeding data and chemical analyses of plants are needed to confirm this finding.

Do infections with parasites and exposure to pollution affect susceptibility to predation in johnny darters (Etheostoma nigrum)?

Johnny darters ( Etheostoma nigrum Rafinesque, 1820) were collected from five localities in the St. Lawrence River in southwestern Quebec to test the effects of natural parasite infections and exposure in situ to pollution on their antipredator behaviour. Three measures of antipredator behaviour were made: (1) capture time (i.e., the time taken to catch individual fish) was used as a proxy for the ability to evade predation, (2) capture order was the order in which fish kept in a single tank were taken from the tank, and (3) flight initiation distance was the distance at which the fish moved when approached by a model predator. Only capture time showed a significant correlation with parasitism or pollution status. A nonparametric permutational multivariate ANOVA showed that capture time was significantly correlated with capture location and the abundance of the brain-encysting trematode Ornithodiplostomum Dubois, 1936. Infection with Ornithodiplostomum sp. may have led to an increase in activity, which would be maladaptive for this cryptic, benthic fish under natural predation conditions. Pollution may have an indirect effect on predator susceptibility in johnny darters, by reducing the abundance of a behaviour-modifying parasite.

Behavioural responses to human-induced environmental change

The initial response of individuals to human-induced environmental change is often behavioural. This can improve the performance of individuals under sudden, large-scale perturbations and maintain viable populations. The response can also give additional time for genetic changes to arise and, hence, facilitate adaptation to new conditions. On the other hand, maladaptive responses, which reduce individual fitness, may occur when individuals encounter conditions that the population has not experienced during its evolutionary history, which can decrease population viability. A growing number of studies find human disturbances to induce behavioural responses, both directly and by altering factors that influence fitness. Common causes of behavioural responses are changes in the transmission of information, the concentration of endocrine disrupters, the availability of resources, the possibility of dispersal, and the abundance of interacting species. Frequent responses are alterations in habitat choice, movements, foraging, social behaviour and reproductive behaviour. Behavioural responses depend on the genetically determined reaction norm of the individuals, which evolves over generations. Populations first respond with individual behavioural plasticity, whereafter changes may arise through innovations and the social transmission of behavioural patterns within and across generations, and, finally, by evolution of the behavioural response over generations. Only a restricted number of species show behavioural adaptations that make them thrive in severely disturbed environments. Hence, rapid human-induced disturbances often decrease the diversity of native species, while facilitating the spread of invasive species with highly plastic behaviours. Consequently, behavioural responses to human-induced environmental change can have profound effects on the distribution, adaptation, speciation and extinction of populations and, hence, on biodiversity. A better understanding of the mechanisms of behavioural responses and their causes and consequences could improve our ability to predict the effects of human-induced environmental change on individual species and on biodiversity.

Mother counts: how effects of environmental contaminants on maternal care could affect the offspring and future generations

Various compounds of anthropogenic origin represent environmental contaminants (EC) that penetrate the food chain and are frequently detected in human milk and maternal blood at the time of delivery. These ECs can affect the development of the fetus and can be transferred to the newborn during lactation. Many studies have used animal models to study the impact of ECs on the development of the nervous system and have reported effects of early exposure on neural and neuroendocrine systems and on behavior, when the exposed animals are tested as adults. Some of these effects persist across generations and may involve epigenetic mechanisms. The majority of these studies in developmental toxicology treat the pregnant or lactating animal with ECs in order to deliver the contaminants to the developing offspring. Almost universally, the mother is viewed as a passive conduit for the ECs, and maternal behavior is rarely assessed. Here we review the literature on the effects of ECs on maternal care and find mounting evidence that important components of the care given to the offspring are affected by maternal exposure to different ECs. Some of these changes in maternal behavior appear to be secondary to changes in the behavior and/or stimulus properties of the exposed offspring, but others are likely to be direct effects of the ECs on the maternal nervous and endocrine systems. Considering the extent to which the quality of maternal care affects the development of the offspring, it becomes imperative to determine the contributions that changes in maternal behavior make to the deficits traditionally ascribed solely to direct effects of ECs on the developing organism. Given the complexity and importance of mother-infant interactions, future research on developmental toxicology must consider the effects of ECs not only on the offspring, but also on the mother and on the interactions and social bond between mother and infant.

Exposure of three generations of the estuarine sheepshead minnow (Cyprinodon variegatus) to the androgen, 17beta-trenbolone: effects on survival, development, and reproduction

Estimating long-term effects of endocrine-disrupting chemicals on a species is important to assessing the overall risk to the populations. The present study reports the results of a 42-week exposure of estuarine sheepshead minnows (Cyprinodon variegatus) to the androgen, 17beta-trenbolone (Tb) conducted to determine if partial-(F0) or single-generation (F1) fish exposures identify multigenerational (F0-F3) effects of androgens on fish. Adult F0 fish were exposed to 0.007, 0.027, 0.13, 0.87,and 4.1 microg Tb/L, the F1 generation to < or =0.87 microg Tb/L, the F2 fish to < or =0.13 microg Tb/L, and the F3 fish to < or =0.027 microg Tb/L. The highest concentrations with reproducing populations at the end of the F0, F1, and F2 generations were 4.1, 0.87, and 0.027 microg Tb/L, respectively. Reproduction in the F0, F1, and F2 generations was significantly reduced at 0.87, 0.027, and 0.027 microg Tb/L, respectively. Fish were significantly masculinized in the F1 generation exposed to 0.13 microg Tb/L or greater. Female plasma vitellogenin was significantly reduced in F0 fish exposed to > or =0.87 microg Tb/L. Gonadosomatic indices of the F0 and F1 generations were significantly increased at 0.87 and 0.13 microg Tb/L in the F0 and F1 generation, respectively, and were accompanied by ovarian histological changes. Reproduction was the most consistently sensitive measure of androgen effects and, after a life-cycle exposure, the daily reproductive rate predicted concentrations affecting successive generations. The present study provides evidence that a multiple generation exposure of fish to some endocrine-disrupting chemicals can result in developmental and reproductive changes that have a much greater impact on the success of a species than was indicated from shorter term exposures.

Chronic exposure of 2,2',4,4'-tetrabromodiphenyl ether (PBDE-47) alters locomotion behavior in juvenile zebrafish (Danio rerio)

In the present study, we used zebrafish (Danio rerio) as a model to address possible effects of chronic exposure of polybrominated diphenyl ether (PBDE) flame retardants on locomotion behavior, body size, and gonad development in fish. Zebrafish were fed food dosed with PBDE-47 (control, solvent control, low, medium, and high dose groups) from 21 days post hatch (dph) to 90 dph. Fish locomotion parameters, including maximum swimming speed, total distance moved, and percent time active, were assessed using a video-based animal movement analysis system. At the end of the exposure, all fish were euthanized for length and weight measurement, and then subjected to either whole fish histological analysis or tissue PBDE-47 measurement. Survival, body size, and gonad histology were similar between the five groups. However, both total swimming distance and percent time active were negatively correlated with tissue PBDE-47 concentration and were significantly lower in the high dose group. Tissue levels of PBDE-47 in the exposed fish were comparable to that reported in previous field studies. In summary, this study showed that developmental exposure of PBDE-47 at an ecologically relevant level altered locomotion behavior without affecting body size or gonad development of zebrafish.

Concentrations of 17 elements, including mercury, and their relationship to fitness measures in arctic shorebirds and their eggs

Exposure to contaminants is one hypothesis proposed to explain the global decline in shorebirds, and this is of particular concern in the arctic. However, little information exists on contaminant levels in arctic-breeding shorebirds, especially in Canada. We studied potential contaminants in three biparental shorebird species nesting in Nunavut, Canada: ruddy turnstones (Arenaria interpres), black-bellied plovers (Pluvialis squatarola) and semipalmated plovers (Charadrius semipalmatus). Blood, feathers and eggs were analyzed for As, Be, Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Sb, Se, Tl, V, and Zn. We assessed whether element concentrations a) differed among species and sexes, b) were correlated among pairs and their eggs, and c) were related to fitness endpoints, namely body condition, blood-parasite load, nest survival days, and hatching success. Non-essential elements were found at lower concentrations than essential elements, with the exception of Hg. Maximum Hg levels in blood approached those associated with toxicological effects in other bird species, but other elements were well below known toxicological thresholds. Reproductive success was negatively correlated with paternal Hg and maternal Pb, although these effects were generally weak and varied among tissues. Element levels were positively correlated within pairs for blood-Hg (turnstones) and feather-Ni and Cr (semipalmated plovers); concentrations in eggs and maternal blood were never correlated. Concentrations of many elements differed among species, but there was no evidence that any species had higher overall exposure to non-essential metals. In conclusion, whereas we found little evidence that exposure to the majority of these elements is leading to declines of the species studied here, Hg levels were of potential concern and both Hg and Pb warrant further monitoring.

An endocrine disrupting chemical changes courtship and parental care in the sand goby

Endocrine disrupting chemicals (EDCs) are a diverse group of compounds that can mimic, block or modulate the synthesis of natural hormones. They are known to cause impairment of reproduction of aquatic organisms at very low concentrations. The aim of this study was to examine how exposure from 10 to 31 days to 17alpha-ethinyl estradiol (EE2, 41 ng L(-1)) affects the courtship and parental care behaviour of male sand gobies (Pomatoschistus minutus). The sand goby exhibits a polygynous mating system, where males compete for females and provide paternal care. First, male courtship performance towards a stimulus female was recorded with video camera. Secondly, after the male had received eggs his parental care behaviour was video recorded. In addition to behavioural endpoints, we measured the expression of hepatic vitellogenin (Vtg) and zona radiata protein (Zrp) mRNA, as well as common somatic indices. Our study shows that exposure to EE2 affected male fanning behaviour during both courtship and parental care. Interestingly, small exposed males increased their courtship fanning to similar levels as larger control males. However, during parental care egg fanning was not related to male size, and all exposed males fanned more than control males. The EE2-exposure induced Vtg and Zrp mRNA expression in males and decreased hepatosomatic index (HSI), and increased gonadosomatic index (GSI). Females prefer males that fan more, which will favour the small EDC exposed males. This may lead to mating that favours males that are not strong enough to tend the eggs until they hatch, thus decreasing the reproductive success of individuals.

Anthropogenic pollutants: a threat to ecosystem sustainability?

Pollutants, including synthetic organic materials and heavy metals, are known to adversely affect physiological systems in all animal species studied to date. While many individual chemicals can perturb normal functions, the combined actions of multiple pollutants are of particular concern because they can exert effects even when each individual chemical is present at concentrations too low to be individually effective. The biological effects of pollutants differ greatly between species reflecting differences in the pattern of exposure, routes of uptake, metabolism following uptake, rates of accumulation and sensitivity of the target organs. Thus, understanding of the effects of pollutants on wildlife and ecosystems will require detailed study of many different species, representing a wide range of taxa. However, such studies can be informed by knowledge obtained in more controlled conditions which may indicate likely mechanisms of action and suitable endpoint measurements. Responses may be exacerbated by interactions between the effects of pollutants and environmental stressors, such as under-nutrition or osmotic stresses and so changes in such variables associated with climatic changes may exacerbate physiological responses to pollutant burdens.

Effects of chronic exposure to nonylphenol on locomotor activity and social behavior in zebrafish (Danio rerio)

Nonylphenol (NP), a xenoestrogen ubiquitously found in aquatic ecosystems, is of high environmental concern. The present work assessed the effects of exposure to NP on locomotor activity and social behavior in male and female zebrafish (Danio rerio), to evaluate the possible hazard of NP to fish behavior and to pursue a potential biomarker of NP contamination. Fish were randomly divided into six groups. Five groups were receiving 0.1, 1, 10, 50 and 100 microg/L nominal concentrations of NP for 60 days, respectively. A sixth control group was given the same treatment as the other five groups, but no NP. Locomotor activity, aggressive behavior, group preference and leaving shoal were examined. NP exposure showed marked influence on locomotor activity of the male zebrafish, whereas that of the female was not significantly affected by NP. Aggressive behavior and group preference were significantly affected by NP exposure in both male and female groups. Locomotor activity and aggressive behavior of the male and group preference of both male and female zebrafish were clearly inhibited at 100 microg/L NP. No significant alteration in leaving shoal was observed under NP exposure. The results suggested that changes in locomotor activity and aggressive behavior of the male and group preference of both male and female may be used as an ecologically relevant integrative biomarker of NP contamination.

Sand goby (Pomatoschistus minutus) males exposed to an endocrine disrupting chemical fail in nest and mate competition

Endocrine disrupting chemicals (EDCs) are a widely studied group of chemicals that interfere with the endocrinology of organisms. So far, few studies have demonstrated the effect of EDCs on the reproductive behavior of aquatic wildlife. Here we show that sand goby males' (Pomatoschistus minutus) success in mating competition greatly decreases after an exposure for 7 to 24 days to 17alpha-ethinyl estradiol (EE2, measured concentration 4 ng L(-1)). The sand goby exhibits a polygynous mating system with male parental care, in which males compete for nest sites and females. The aim of this study was to test how EE2 exposure affects the ability of males to compete for breeding resources, i.e. nest sites and mates. First, EE2 exposed males competed over a nest site against a non-exposed, control male of the same size. Secondly, we examined male courtship behavior and female mate preferences for EE2 exposed males and similar-sized non-exposed, control males. In addition to the behavioral experiments we determined the zona radiata protein (Zrp) mRNA gene expression and measured morphometric indicators of sexual maturation. Our study revealed that EE2 treated males were not able to acquire or defend a nest site. Additionally, EE2 treated males spent significantly less time in active courtship and nest leading behavior than control males. As a result, females clearly preferred to mate with control males. However, we found no significant differences in Zrp mRNA expression or the morphometric indicators between treatments. Our study illustrates that exposure to this EDC can greatly reduce the chances of an individual reproducing successfully. Moreover, it demonstrates that severe behavioral effects can be seen before any effects are detectable at the molecular or morphometric level.

Disruption of sexual selection in sand gobies (Pomatoschistus minutus) by 17alpha-ethinyl estradiol, an endocrine disruptor

In aquatic environments, endocrine disrupting chemicals (EDCs) that interfere with the reproductive physiology of males form a threat to the reproduction of populations. This is often manifested as decreased sexual performance or sterility among males. We show that exposure to EDCs can directly affect the mating system of a marine fish, the sand goby (Pomatoschistus minutus). We exposed males for 1 to 4 weeks to two different concentrations (5 ng L(-1) and 24 ng L(-1)) of 17alpha-ethinyl estradiol (EE2); a synthetic compound mimicking estrogen and a water control. The sand goby exhibits a polygynous mating system, in which male mating success is typically skewed towards the largest males, resulting in strong sexual selection for increased male size. Our experiment shows that when males have been exposed to EE2, male size has a smaller effect on mating success, resulting in weaker sexual selection on male size as compared to the control. There was an interaction between treatment and exposure time on the expression of vitellogenin and zona radiata protein mRNAs. Males exposed to high EE2 reached much higher expression levels than males exposed to low EE2. Of the somatic markers, the hepatosomatic index was lower in males exposed to high EE2 than in the low EE2 and control males. Our results suggest that exposure to EDCs can have effects on the mating system before physiological changes are observable. These effects can be of profound nature as they interfere with sexual selection, and may in the long run lead to the loss of traits maintained through sexual selection.

Relating disparity in competitive foraging behavior between two populations of fiddler crabs to the subcellular partitioning of metals

Behavioral changes in aquatic organisms such as reduced prey capture and decreased mobility have been linked to exposure to contaminants in the field. The purpose of this study was to compare competitive foraging and dominance behaviors of two populations of the fiddler crab, Uca pugnax, and to examine the relationship between tissue metal residues and observed differences in behavior. Foraging behavior (number of total scoops and scoops on a protein-rich patch) and dominance behavior (percentage of successful attacks) of fiddler crabs from an impacted site (Meredith Creek, New York) and a reference site (Tuckerton, New Jersey) were compared in the laboratory. Tuckerton (Tk) crabs were found to have twice the number of total scoops (70 vs. 38 scoops, p < 0.05) and three times the number of scoops on patch (34 vs. 10 scoops, p < 0.05) than Meredith (Me) crabs. No difference was observed between crab populations in the number of successful attacks (i.e., fights over the protein-rich patch). Analyses of total metal body burdens and metals associated with various subcellular fractions showed that, when compared with Tk crabs, Me crabs had higher levels of Ag, Cd, Cu, Ni, and Se in the heat-denatured proteins (HdeP) (i.e., enzymes). Metal bioaccumulation can have inhibitory effects on enzymes, which play an essential role in the regulation of various biochemical, metabolic, and physiological activities in crustaceans. This study suggests that there is a relationship between the accumulation of metals in HdeP (i.e., enzymes) and impairment of competitive foraging behavior in fiddler crabs. Additionally, this study shows that when compared with dominance behavior, foraging behavior is a more sensitive indicator of metal exposure and might be used as an end point in ecotoxicology studies.

The organophosphorous pesticide, fenitrothion, acts as an anti-androgen and alters reproductive behavior of the male three-spined stickleback, Gasterosteus aculeatus

Fenitrothion (FN) is a widely used organophosphorous pesticide that has structural similarities with the clinical anti-androgen flutamide. The potential for FN to act as an anti-androgen (at exposures of 1, 50, and 200 microg FN/l over a 26-day period) was assessed in male three-spined sticklebacks, Gasterosteus aculeatus, by measuring kidney spiggin concentration, nest-building, and courtship behavior. Spiggin is the glue protein that male sticklebacks use to build their nests and is directly controlled by androgens. FN exposure significantly reduced spiggin production as well as nest-building activity. It also adversely affected courtship--especially the 'zigzag dance' and biting behavior of the males. FN thus appears to have anti-androgenic effects on both the physiology and behavior of the male stickleback.

The model anti-androgen flutamide suppresses the expression of typical male stickleback reproductive behaviour

Over the past 15 years considerable attention has been given to the presence in the environment of endocrine disrupting chemicals (EDCs) that may have harmful effects on organisms. Specific test guidelines for the detection of EDCs used for short-term fish screening assays have been developed by the Organisation for Economic Cooperation and Development (OECD). Compared to the core species used in the OECD guidelines, the three-spined stickleback (Gasterosteus aculeatus) has an additional and unique endpoint for (anti-)androgenic substances through the androgen-dependent glue protein (spiggin) used in the nest building. Here we describe a specific behavioural assay that was developed in parallel to the OECD protocol, utilising unique behavioural features of sticklebacks. In the assay, a photoperiod of 16L:8D (light:dark) and a temperature of 17+/-1 degrees C was used to induce breeding in quiescent male sticklebacks that were simultaneously exposed for a 21-day period to the mammalian anti-androgen flutamide (FL) at 100, 500 and 1000 microg/l (plus a water control). Spiggin production and the reproductive behaviour (nest building and courtship) of male sticklebacks were the main measured endpoints. The control fish entered an active breeding cycle including nest building and courtship behaviours as expected due to the stimulating temperature and photoperiodic conditions. The FL-exposed males showed significantly lower spiggin levels at 500 and 1000 microg/l. In addition, there was a significant decrease in the number of nests built by the FL-treated males at 100 microg/l with no nest built at 500 and 1000 microg/l. Finally, FL affected the courtship behaviour of the males with a significant reduction of the number of zigzags towards the female. When the breeding status of the stickleback males is controlled, the behavioural assay developed here is a suitable tool for the detection of androgen antagonists.

Scents and scents-ability: pollution disrupts chemical social recognition and shoaling in fish

Chemical cues are of enormous importance in mediating the behaviour of animals, enabling them to navigate throughout their habitats, to detect the presence of predators or prey and for social recognition-identifying and discriminating between conspecifics. In many species of freshwater fish, social recognition is known to be based primarily on chemical cues. Such recognition mechanisms are vulnerable to disruption by the presence of anthropogenic contaminants in the aquatic environment. Here we show that acute exposure to low, environmentally relevant dosages of the ubiquitous contaminant, 4-nonylphenol, can seriously affect social recognition and ultimately social organization in fishes. A 1 hour 0.5 microgl-1 dose was sufficient to alter the response of members of a shoaling fish species (juvenile banded killifish, Fundulus diaphanus) to conspecific chemical cues. Dosages of 1-2 microgl-1 caused killifish to orient away from dosed conspecifics, in both a flow channel and an arena. Given the overall importance of shoaling as an adaptive strategy against predators and for locating food, it is likely that its disruption by anthropogenic contaminants would have serious implications for fishes' fitness.

Developmental exposure to low-dose estrogenic endocrine disruptors alters sex differences in exploration and emotional responses in mice

Estrogenic endocrine disruptors (EEDs) are naturally occurring or man-made compounds present in the environment that are able to bind to estrogen receptors and interfere with normal cellular development in target organs and tissues. There is mounting evidence that EEDs can interfere with the processes of sexual differentiation of brain and behavior in different animal models. We investigated the effects of maternal exposure to EEDs, at concentrations within the range of human exposure and not patently teratogenic, on behavioral responses of male and female house mice (Mus musculus domesticus) before and after puberty. Pregnant dams were trained to spontaneously drink daily doses of corn oil with or without the estrogenic plastic derivative, bisphenol A (BPA 10 microg/kg), or the estrogenic insecticide methoxychlor (MXC 20 microg/kg) from gestation day 11 to postpartum day 8. Their male and female offspring were examined at different ages to examine several components of explorative and emotional behaviors in 3 experimental paradigms: a novelty test before puberty and, as adults, a free-exploratory open-field test and the elevated plus maze test. The main results are sex differences in control mice on a number of behavioral responses at both ages and in all experimental paradigms, while perinatal exposure to BPA or MXC decreased or eliminated such sex differences. The present findings are evidence of long-term consequences of developmental exposure to BPA and MXC on neurobehavioral development and suggest a differential effect of low-dose exposure to these estrogenic chemicals in males and females.

Living in the city: Resource availability, predation, and bird population dynamics in urban areas

This article explores factors that shape population structure in novel environments that have received scant theoretical attention: cities. Urban bird populations exhibit higher densities and lower diversity. Some work suggests this may result from lower predation pressure and more predictable and abundant resources. These factors may lead to populations with few winners and many losers regarding access to food, body condition, and reproductive success. We explore these hypotheses with an individual-energy-based competition model with two phenotypes of differing foraging ability. We show that low frequency resource fluctuations favor strong competitors and vice versa. We show that low predation skews equilibrium populations in favor of weak competitors and vice versa. Increasing the time between resource pulses can thus shift population structure from weak to strong competitor dominance. Given recent evidence for more constant resource input and lower predation in urban areas, the model helps understand observed urban bird population structure.

Effect of malathion on survival, growth, and food consumption of Indian cricket frog (Limnonectus limnocharis) tadpoles

The effects of short-term exposure (28 days) of free-feeding Limnonectus limnocharis (Indian cricket frog) tadpoles to field concentrations of malathion were investigated. This frog species is a major biotic component of the agroecosystems of the Western Ghats (13 degrees 18', 75 degrees 25' and 13 degrees 22', 75 degrees 28'), where malathion (diethyl [(dimethoxy phosphino thioyl] butanediote), an organophosphate pesticide, is being used extensively. Although malathion is known to cause nonreversible acetylcholine inhibition and diminishes activity, growth and development in amphibian tadpoles, such data on Indian amphibian species are lacking. In the present study, increments in the following were used to assess such an impact: tadpole growth; increase in total length, body length, tail length, and body weight; and food consumption. The different concentrations of malathion employed were 500, 1000, 1500, 2000, and 3000 mug L(-1). Malathion exposure produced significant effects on all measured parameters. Tadpole survival decreased from 20 to 6 tadpoles, with an increase in concentration followed by a decrease in growth. Food consumption of surviving tadpoles also decreased (0.067 mg.g(-1).d(-1) to 0.0075 mg.g(-1).d(-1)) with increased malathion. Decreased food consumption, growth, and development of L. limnocharis tadpoles with an increase of malathion concentration (within field concentration range) over temporal scale reveal the possible threat to this species in the agroecosystems of the Western Ghats.

Behavioral changes in fish exposed to phytoestrogens

We investigated the behavioral effects of exposure to waterborne phytoestrogens in male fighting fish, Betta splendens. Adult fish were exposed to a range of concentrations of genistein, equol, beta-sitosterol, and the positive control 17beta-estradiol. The following behaviors were measured: spontaneous swimming activity, latency to respond to a perceived intruder (mirror reflection), intensity of aggressive response toward a perceived intruder, probability of constructing a nest in the presence of a female, and the size of the nest constructed. We found few changes in spontaneous swimming activity, the latency to respond to the mirror, and nest size, and modest changes in the probability of constructing a nest. There were significant decreases, however, in the intensity of aggressive behavior toward the mirror following exposure to several concentrations, including environmentally relevant ones, of 17beta-estradiol, genistein, and equol. This suggests that phytoestrogen contamination has the potential to significantly affect the behavior of free-living fishes.